Electrical resistance composition and resistance element

ABSTRACT

An electrical resistance composition has been provided using particles of ruthenium oxide which are coated with niobium and/or niobium oxide, and a glass frit.

[ ELECTRICAL RESISTANCE COMPOSH'THON [56] References Cited AND RESISTANCE ELEMENT UNITED STATES PATENTS [75] Inventors: Eiiclhi Asada, Sakuradai; Minm'u 3,622,367 11/1971 Haag 117/100 B Nakagome, Tokyo, both of Japan 3,352,797 11/1967 Kim 1 117/227 3,031,344 41962 Sh 1 a1... 117100 B [73] Assigneel $11M Emmi! mdusmes 3,562,122 2/1971 1111;; 242 472 Tokyo, Japan 3,637,344 1/1972 Thompson 252/472 Filed: Nov. 1971 3,637,530 1/1972 Cassale 117/201 1211 Appl- N05 199,462 Primary Examiner-A1fred L. Leavitt Assistant ExaminerM. F. Esposito 30 Feral-lg Application Unity Data Att0rney-Norma.n F. Oblon et a1.

Nov. 17, 1970 Japan 45/101207 [57] ABSTCT 52 us. an. 117/227, 117/100 B, 252/512, An electrical resistance composition has been pm 1 252/514 vided using panicles of ruthenium oxide which are [51] Int. Cl. 1B l/02, B050 7/14 coated with niobium and/or niobium oxide and a glass 58 Field 01 Search 117/227, 100 B;

5 Claims, N0 Drawings 1 ELECTRICAL RESISTANCE COMPOSITION AND RESISTANCE ELEMENT BACKGROUND OF THE INVENTION 1. Field Of The Invention The present invention relates to electrical resistance compositions and more particularly to an improved resistance composition which contains both fine composite particles of ruthenium oxide and powdered glass frit, which, upon firing, result in a resistor having a very low level of noise, reasonably minor fluctuations in initial resistance values and excellent TCR values.

This invention also relates to fired electrical resistor elements which are obtainable by applying the said composition material onto a heat-resistant insulating base.

2. Description Of PriorArt It is now well known that ruthenium oxide can be used in forming fired electrical resistors (US. Pat. No. 3,271,193 and British Pat. No. 1,002,793), and that the ruthenium oxide will be less readily diffused into molten glass fractions during firing, as compared with Ag-Pd or AglPdO. Moreover, ruthenium oxide resistors are generally characterized by satisfactory resistance value stability and low resistor noise.

One difficulty which has been observed in-the' prior art resistors which use oxides of ruthenium, iridium or rhodium as conductive fractions, is that these metal oxides are not uniformly dispersed, and hence the resulting resistors suffer from deficient storage stability characteristics and from an appreciable fluctuation in initial resistance values.

In an effort to overcome this disadvantage, US Pat. No. 3,326,645 disclosed the use of organic derivatives or resinates of ruthenium instead of the oxide. This expedient, however, was found to have even less storage stability due to the origin of the component, and had the additional disadvantage of the need for a quite intricate preparation scheme. Moreover, the resulting composition was found to have insufficient printability due to its relatively low metal content.

SUMMARY OF THE INVENTION Accordingly, it is one object of this invention to provide an electrical resistance composition for electrical resistance elements, which are characterized by uniform initial resistance values, low electrical current noise, and excellent temperature coefficiency of resistance.

This and other objects of this invention, as will hereinafter become more apparent, can be attained by providing an electrical resistance composition which comprises particles of ruthenium oxide coated with niobium and/or niobium oxide, a glass frit and an organic vehicle for binding said materials.

DETAILED DESCRIPTION OF THE INVENTION The ratio of ruthenium oxide to the niobium component may suitably be present in the range of l to about 40 to l, and preferably 4 to about 20 to l. The size of the particles of the ruthenium oxide coated with the niobium or niobium oxide, is usually less than 50 1.0, and preferably less than u in average particle diameter. The ruthenium oxide used can be either RuO or RuO. The glass frit used for thecomposition of this invention can be any of a variety of frit compositions containing PbO, B 0 and SiO (For'example, one suitable frit is 2 lead borosilicate frit 63% PhD, 25% B20 and 12% SiO Especially suitable are any of the conventional lead borosilicate frits of the prior art, particularly those having melting points of between 250 and 1,000C., and preferably between 350 and 900C. The ratio of coated particles to glass frit, is usually between 1 to 99 to 15 and preferably 8 to 60: 92 to 40.

There is no limit on the quantity of organic vehicles which may be used as the binding agent. It should be used in sufficient amounts, however, to form a paste with the other components of the composition.

Suitable organic vehicles which may be used herein include the alcohols, esters, ethers, aromatic hydrocarbons, amides and amines and some plasticizers such as dibutylphthalate, octylphthalate. In addition, cellulose derivatives, resin, asphalt, polyacrylate, epoxy resin, polyesters, polystyrene, polyvinylacetate, melamine .resin, alkyd resin, polyether and their solutions may also be employed as vehicles. In some cases, oily materials of natural origin suchas terpineol, castor oil and other terpenoids may also be used.

In preparing the compositions of this invention, finely powdered ruthenium oxide is dispersed with a niobium organic derivative, in an organic solvent medium. The mixture is then subjected to pyrolysis to yield the niobium or niobium oxide coated ruthenium oxide particles.

Suitable niobium derivatives which may be used in forming the coated particles include niobium pentaethoxide, niobium pentabutoxide, niobium pentaisopentyloxide, niobiumoxy-tributoxide, niobium penta-propoxide, niobium penta-t-butoxide, niobium penta-sec-butoxide, niobium penta-l-ethyl propoxide, niobium penta-l-methyl butoxide, niobium oxytripropoxide, or the like.

These composite particles may alternatively be produced by electroplating, electroless plating, vacuum deposition, or inorganic salt pyrolysis, ontothe ruthenium oxide.

These particles are then mutually dispersed with a glass frit and an appropriate quantity of organic vehicle, in a ball mill, roll mill, kneader, or by other conventional means.

This composite is then coated onto a heat-resistant base by painting, spraying, dipping or roller coating and fired at a temperature within the range of 250 and 1,00O C. optimally from 350-900C. Upon firing, the organic materials (or vehicle) are burned, the glass frit is melted and the other inorganic materials are sintered. Resistance layers having thicknesses of-from 0.5 to 100p, and preferably 3 to 30p. are obtainable in this manner.

Suitable heat-resistant electrically insulating bases onto which the coating may be applied include ceramics of alumina, steatite, forsterite, mullite, titania, barium titanate, magnesia, zirconia, beryllia, thoria, spinal, cordierite, zircon, lithia, pyroceram and glass, quartz, sapphire.

Other additives may be used with the composition of this invention, if necessary, including various metal powders, various metal oxides, various organo-metallic compounds, noble metal powders or noble metal oxides, depending upon the particular characteristics required. Such additional components will. usually be present in amounts of less than 20% by weight, based EXAMPLE 1 50 g. of ruthenium oxide was thoroughly admixed with 56 g. of benzene solution containing 19.2 g. of niobium pentaethoxide, Nb(OC- H and then the mixture was dried followed by pyrolysis to give 58.0 g. of composite powder with the RuO /Nb ratio of 9/1.

EXAMPLE 2 60.2 g. of composite powder was obtained from 50 g. of ruthenium oxide and 71 g. of benzene solution containing 24.3 g. of niobium pentaethoxide, Nb(OC H The RuO /Nb ratio was 7/1.

EXAMPLE 3 59.0 g. of composite powder was obtained from 50 g. of ruthenium oxide and 63 g. of benzene solution containing 21.5 g. of niobium pentaethoxide, Nb(OC H the RuO /Nb ratio was 8/1.

EXAMPLE 4 53.7 g. of composite powder was obtained from 50 g. of ruthenium oxide and 26 g. of xylene solution containing 12.8 g. of niobium pentabutoxide, Nb(OC4Hg)5. The RuO /Nb ratio was 19/1.

EXAMPLE 5 67.9 g. of composite powder was obtained from 50 g. of ruthenium oxide and 125 g. of xylene solution cntaining 61.6 g. of niobium penta-butoxide, Nb(OC H The RuO /Nb ratio was 4/1.

EXAMPLE 6 60.2 g. of composite powder was obtained from 50 g. of ruthenium oxide and 71 g. of benzene solution containing 35.0 g. of niobium penta-butoxide, Nb(OC H The RuO /Nb ratio was 7/1.

EXAMPLE 7 61.9 g. of composite powder was obtained from 50 g. of ruthenium oxide and 83 g. of benzene solution containing 47.1 g. of niobium penta-iso-pentyloxide, Nb [OCH CH CH(CH The RuO /Nb ratio was 6/1.

EXAMPLE 8 64.3 g. of composite powder was obtained from 50 g. of ruthenium oxide and 100 g. of cyclohexane solution containing 56.8 g. of niobium penta-iso-pentyloxide, Nb[OCl-l CH Cl-l(CH The RuO /Nb ratio was 5/1.

EXAMPLE 9 56.0 g. of composite powder was obtained from 50 g. of ruthenium oxide and 42 g. of methyl ethyl ketone solution containing 23.9 g. of niobium penta-isopentyloxide, Nb[OCH CH Cl-l(CH The RuO /Nb ratio was 12/1.

EXAMPLE 10 54.7 g. of composite powder was obtained from 50 g. of ruthenium oxide and 33 g. of methyl ethyl ketone solution containing 1 1.6 g. of niobium oxy-tributoxide, NbO(OC 1-l The RuO /Nb was 15/1.

EXAMPLE 1 1 54.1 g. of composite powder was obtained from 50 g. of ruthenium oxide and 29 g. of cyclohexane solution containing 10.2 g. of niobium oxy-tributoxide, NbO- (OC H The RuO /Nb ratio was 17/1.

EXAMPLE 12 61.9 g. of composite powder was obtained from 50 g. of ruthenium oxide and 83 g. of cyclohexane solution containing 29.3 g. of niobium oxy-tributoxide, NbO- (OC H9) The RuO /Nb ratio was 6/1.

EXAMPLE 13 58.0 g. of composite powder was obtained from 50 g. of ruthenium oxide and 56 g. of xylene solution containing 23.4 g. of niobium pentapropoxide, Nb(OC H The RuO /Nb ratio was 9/1.

EXAMPLE 14 60.2 g. of composite powder was obtained from 50 g. of ruthenium oxide and 71 g. of benzene solution containing 35.0 g. of niobium penta-tert-butoxide, Nb[OC(CH The RuO /Nb ratio was 7/1.

EXAMPLE 15 59.0 g. of composite powder was obtained from 50 g. of ruthenium oxide and 63 g. of benzene solution containing 31.1 g. of niobium penta-secbutoxide, Nb(O- sec-C H The RuO /Nb ratio was 8/1.

EXAMPLE 16 53.7 g. of composite powder was obtained from 50 g. of ruthenium oxide and 26 g. of xylene solution containing 14.8 g. of niobium penta-l-ethyl propoxide, Nb[OCH(C H )CH CH The RuO /Nb ratio was 19/1.

EXAMPLE 17 67.9 g. of composite powder was obtained from 50 g. of ruthenium oxide and g. of cyclohexane solution containing 61.6 g. of niobium penta-iso-butoxide, Nb(O-iso-C l-1 The RuO /Nb ratio was 4/ 1.

EXAMPLE 18 60.2 g. of composite powder was obtained from 50 g. of ruthenium oxide and 71 g. of cyclohexane solution containing 35.0 g. of niobium penta-tert-butoxide, Nb(O-tert-C 1-l The RuO /Nb ratio was 7/1.

EXAMPLE 19 61.9 g. of composite powder was obtained from 50 g. of ruthenium oxide and 83 g. of methyl ethyl ketone solution containing 47.1 g. of niobium penta l-methylbutoxide, Nb[OCH(Cl-l )C H-,] The RuO /Nb ratio was 6/1.

EXAMPLE EXAMPLE 21 I I parts composite particle,RuO /Nb=9/l (obtained from Example l) 14 powdered glass frit 62 cellulose solution 24 A paste-like composition material was prepared from the above components bythorough admixing in a ball niill.

EXAMPLE 22 The same procedure as in Example 2l"was applied for the following components:

. parts composite particle,RuO,/Nb=7ll (obtained from Example 2) 9 powdered glass frit 66 cellulose solution EXAMPLE 23 The same procedure as in Example 21 was applied for the following components:

. parts composite particle,RuO /Nb=9/l (obtained from Example l) 13 powdered glass frit 63 cellulose solution 24 EXAMPLE 24 The same procedure as in Example 21 was applied for the following components:

parts composite particle,RuO /Nb=7/l (obtained from Example 2) l4 powdered glass frit 63 polystyrene solution 23 EXAMPLE 25 The same procedure as in Example 21 was applied for the following components:

parts composite particle.RuO,/Nb=9/l (obtained from Example 1) ll powdered glass frit 65 alkyd resin solution 24 EXAMPLE 26 The same procedure as in Example 21 was applied for the following components:

, 1 v parts composite particle,RuO,/Nb=9/l (obtained from Example 1) l5 7 powdered glass frit 60 melamine-alkyd solution 25 EXAMPLE 27 The same procedure as in Example'2l was applied for the following components:

parts composite particle,RuO,/Nb=7/l (obtained from Example 2) ll powdered glass frit 65. cellulose solution 24 EXAMPLE 28 The same procedure as in Example 21 was applied for the following components:

' parts composite particle,RuO /Nb=8/ I (obtained from Example 3) l5 powdered glass frit 61 "polystyrene solution 24 EXAMPLE 29 The same procedureas in Example 21 was applied for the following components:

parts composite particle,RuO /Nb=8/l (obtained from Example 3) l2 powdered glass frit 63 alkyd resin' solution 25 EXAMPLE 30 The same procedure as in Example 21 was applied for the following components:

e parts composite particle,RuO,/Nb=l9/l (obtained from Example 4) 6 powdered glass frit 69 melamine-alkyd solution 25 EXAMPLE 3 l The same procedure as in Example 21- was applied for the following components:

} parts composite particle,RuO /Nb=4/l (obtained from Example 5) 45 powdered glass frit 30 cellulose solution 25 EXAMPLE 32 The same procedure as in Example 21 was applied for the following components:

' parts composite particle,RuO /Nb=7/l(obtained from Example 6) l5 powdered glass frit 60 polystyrene solution 25 EXAMPLE 33 The same procedure as in Example 21 was applied for the following components:

parts composite particle,RuO /Nb=6/l (obtained i from Example 7) l9 powdered glass frit 56 alkyd resin solution EXAMPLE 34 The same procedure as in- Example 21 was applied for the following components:

parts composite particle,RuO,/Nb=5/ I (obtained from Example 8) 41 powdered glass frit 34 melamine-alkyd solution 25 EXAMPLE 35 The same procedure as in Example 21 was applied for the following components:

parts composite particle.RuO,/Nb=12l1 (obtained from Example 9) l l powdered glass frit 64 cellulose solution 25 EXAMPLE 36 The same procedure as in Example 21 was applied for the following components:

parts composite partie1e.RuO,/Nb=l5/l (obtained from Example 10) powdered glass frit 60 polystyrene solution 25 EXAMPLE 37 The same procedure as in Example 21 was applied for the following components:

parts composite particle,RuO,/Nb=1 7/1 (obtained from Example 11) 9 powdered glass frit 66 alkyd resin solution 25 EXAMPLE 38 The same procedure as in Example 21 was applied for the following components:

parts composite particle,RuO /Nb=6/l (obtained from Example 12) 22.5 powdered glass frit 52.5 melamine-alkyd solution 25 EXAMPLE 39 The same procedure as in Example 21 was applied for the following components:

parts composite particle,RuO;/Nb=9/l (obtained from Example 13) 13.5 powdered glass frit 61.5 cellulose solution 25 EXAMPLE 40 The same procedure as in Example 21 was applied for the following components:

parts composite partic1e,RuO /Nb=7/1 (obtained from Example 14) 24 powdered glass frit 51 polystyrene solution 25 indium oxide 3 EXAMPLE 41 The same procedure as in Example 21 was applied for the following components:

parts composite particlc,RuO,/Nb=8/l(obtained from Example 15) 19 powdered glass frit 56 alkyd resin solution 25 tantalum oxide 0 EXAMPLE 42 The same procedure as in Example 21 was applied for the following components:

parts composite purtic1e.Ru0,/Nb=l9ll (obtained The same procedure as in Example 21 was applied for the following components:

parts composite particle,RuO,/Nb=4/ 1 (obtained from Example 17) 30 powdered glass frit 45 cellulose solution 25 silver-resinate l0 EXAMPLE 44 The same procedure as in Example 21 was applied for the following components:

parts composite partic1e,RuO,/Nb=7/ 1 (obtained from Example l8) l7 powdered glass frit 58 polystyrene solution 25 platinum powder 3 EXAMPLE 45 The same procedure as in Example 21 was applied for the following components:

composite particle,RuO,/Nb=6/l(obtained from Example 19) 25 powdered glass frit 50 alkyd resin solution 25 osmium oxide 2 EXAMPLE 46 The same procedure as in Example 21 was applied for the following components:

parts composite particle.RuO,/Nb=5ll(obtained from Example 20) 26 powdered glass frit 49 melamine-alkyd solution 25 iridium powder 5 The compositions of the present invention were compared with those of the prior art as follows:

Reference 47 Powdered RuO, Powdered Nb O 4 Powdered glass frit 65 Organic vehicle 24 parts 7 Above components were treated analogously to Example 21.

Reference 48 parts Powdered RuO l2 Powdered Nb- OB 1 Powdered glass frit 63 Organic vehicle 24 Above components were treated analogously to Example 21.

Reference 49 parts Powdered RuO 36 Powdered Nb,O 9 Powdered glass frit 30 Organic vehicle 25 Above components were treated analogously to Example 21.

Reference 50 parts Powdered RuO, 23 Powdered Nb O 2 Powdered glass frit 50 Organic vehicle Above components were treated analogously to Example 21.

Reference 51 parts Powdered RuO, 27 Powdered Nb O, 3 Powdered glass frit 45 Organic vehicle 25 TABLE 1 Initial Resistance Example No. Max. ((1) Min. ((2) Average ((1.) 21 16.0 24.0 15.0 22 12.0 8.0 10.0 23 19.0 15.0 17.0 24 14.0 10.0 12.0 25 19.0 17.0 18.0 26 10.6 8.0 9.6 27 8.9 8.1 85.0 28 14.0 12.0 13.0 29 53.0 41.0 47.0 30 2.6 2.1 2.3 31 26.0 24.0 25.0 32 40.0 36.0 37.0 33 8.5 7.6 8.2 34 98.0 95.0 96.0 35 80.0 75.0 78.0 36 26.0 23.0 25.0 37 265.0 248.0 255.0 3.7 3.4 3.6 39 50.0 45.0 47.0 40 2.7 2.4 2.6 41 12.0 11.0 11.2 42 201.0 186.0 198.0 43 262.0 248.0 250.0 44 16.0 14.0 15.0 45 890.0 858.0 870.0 46 723.0 682.0 709.0

Reference: 47 74.0 12.0 43.0 48 22.0 6.0 r 14.0 49 48.0 11.0 28.0 50 480.0 111.0 270.0 51 970.0 311.0 540.0

TABLE 2 TCR & Noise Parameter Example No. TCR (ppm/C.) Noise Parameter (dB) 21 96.0 12.0 22 43.0 -l4.0 23 32.0 10.0 24 18.0 13.0 25 84.0 9.0 26 76.0 15.0 27 45.0 --9.5 28 48.0 t "12.5 29 28.0 9.8 30 97.0 +3.0 31 92.0 35.0 32 5.0 -10.0 33 12.0 13.0 34 80.0 -32.0 35 65.0 7.0 36 20.0 21.0 37 73.0 1.0

Reference:

The TCR values and noise parameters were obtained by use of a Wheatstone bridge and Quen-Tech noise meter, respectively. As can be seen from the above tables, the initial resistance values obtained from the present composition showed only a minor deviation as compared with those of References 47-51 (from the prior art). Analogous results can also be seen as regards TCR and noise parameter given in Table 2.

These good results are believed to be due to the use of the composite structure which facilitates both uniform dispersion of the particles in the molten state and facilitates the formation of an evenly fired surface with equalized and fully reproducible characteristics.

The use of niobium oxide is believed to be particularly advantageous in that it is known that this material is an effective additive for controlling TCR. In the composite form, this material has been found to be especially effective.

Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention.

What is claimed as new and desired to be secured by letters patent is: t

1. An electrical resistance composition which comprises particles of ruthenium oxide which are coated with niobium, niobium oxide or mixtures thereof wherein the ratio of ruthenium oxide to niobium component is from 1 to 40:1.

2. The composition of claim 1, wherein the ratio of ruthenium oxide to niobium component is from 1 to 40:1, and the particle size is less than 5011..

3. The composition of claim 1, wherein the ratio of ruthenium oxide to niobium component is from 4 to 20:1.

41. An electrical resistance element which comprises a high temperature resistant, electrically nonconductive substrate having a film of resistance material coated thereon wherein said'resistance material comprises a sintered mixture of ruthenium oxide coated with niobium, niobium oxide or mixtures thereof wherein the ratio of ruthenium oxide to niobium component is from 1 to 40:1, and a glass frit.

5. The element of claim 4, wherein the ratio of coated ruthenium oxide particles to said glass frit is from 1 to :99 to 15. 

2. The composition of claim 1, wherein the ratio of ruthenium oxide to Niobium component is from 1 to 40:1, and the particle size is less than 50 Mu .
 3. The composition of claim 1, wherein the ratio of ruthenium oxide to niobium component is from 4 to 20:1.
 4. An electrical resistance element which comprises a high temperature resistant, electrically non-conductive substrate having a film of resistance material coated thereon wherein said resistance material comprises a sintered mixture of ruthenium oxide coated with niobium, niobium oxide or mixtures thereof wherein the ratio of ruthenium oxide to niobium component is from 1 to 40:1, and a glass frit.
 5. The element of claim 4, wherein the ratio of coated ruthenium oxide particles to said glass frit is from 1 to 85:99 to
 15. 